Ukraine asks IAEA to close sky above nuclear sites to prevent act of 'nuclear terrorism' by Russia

Ukraine has asked the the International Atomic Energy Agency (IAEA) to seek NATO help with closing the air over Ukrainian nuclear sites to prevent an act of "nuclear terrorism" by Russia, Kyiv's energy ministry said on Thursday.

Ukraine has 15 nuclear reactors and Russia has already seized the defunct Chernobyl nuclear power plant during its week-long invasion of its neighbour.

"We insist on taking urgent decisive actions," the Ukrainian ministry said in a statement.

Russia's invasion of Ukraine entered its second week on Thursday with its main assault force halted north of the capital Kyiv and several cities enduring heavy Russian bombing.

The humanitarian crisis also worsened, with more than one million refugees now having fled Ukraine, the United Nations said.

Hundreds of Russian soldiers and Ukrainian civilians have been killed since Putin sent his troops over the border last Thursday.

Russia itself has been plunged into isolation never before experienced by an economy of such size.

Despite an initial battle plan that Western countries said was aimed at swiftly toppling the Kyiv government, Russia has captured only one Ukrainian city so far - the southern Dnipro River port of Kherson, which its tanks entered on Wednesday.

Russia has shifted tactics, escalating its bombardment of major cities. Swathes of central Kharkiv, a city of 1.5 million people, have been blasted into rubble.